/*
    This file is part of the substandard lisp implementation of Standard Lisp
    Copyright (C) 2011 Nicky Nickell

    substandard lisp is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

(de liter (u)
  (if (memq u '(!A !B !C !D !E !F !G !H !I !J !K !L !M
                !N !O !P !Q !R !S !T !U !V !W !X !Y !Z
                !a !b !c !d !e !f !g !h !i !j !k !l !m
                !n !o !p !q !r !s !t !u !v !w !x !y !z))
    t
    nil))

/*---
name: liter

doc: |
  explaining what liter is / how it is used!

tests: |
  (liter 9) -> NIL
  (liter 'a) -> T
  (liter 'aaa) -> NIL
...*/
